The use of high mast lighting has out-paced the requirements and development of necessary and proper safety features. Most of the raising and lowering devices used in conjunction with high mast lighting may be restrained, braked, locked or otherwise secured in the raised and lowered positions. These raising and lowering devices do not however provide adequate safety during the course of raising and lowering the increasingly heavy carrying rings and lighting fixtures, nor do they provide safety under static conditions.
High mast lighting fixtures are variously suspended and controlled from the three cables that are affixed thereto and pass over capstan arrangements at the top of the mast and extend downwardly inside the mast for attachment to anchoring means of some kind. When the lighting fixtures are to be lowered for cleaning, repair or replacement it is necessary to manipulate the anchoring means so that a braking force can be applied as the lighting fixtures are lowered. Following the maintenance procedure, the lighting fixtures must be raised to the top of the mast and the system secured against tampering and accidental release.
In U.S. Pat. No. 3,696,241, a tower and support for high mast lighting fixtures is disclosed which employs an elongated counter-weight at the cable ends inside the tower, much like the counter-weight used in elevators. A power winch is employed for use with a lift cable running over a sheave mounted in the top of the tower and back to the counter-weight. The power winch raises and lowers the counter-weight and the lighting fixtures as desired. No safety provisions are provided and failure of the power winch or supporting cables can present a dangerous situation for the workmen. A similar system is described in U.S. Pat. No. 3,686,498 wherein the counter-weight is not permanently attached to the cable system and is detached during raising and lowering of the lighting fixtures. Here again safety depends on the power winch device.
U.S. Pat. No. 3,801,813, by the instant inventor, discloses a combination mast and light fixture raising and lowering apparatus wherein the supporting cables pass over capstans at the top of the mast and downward through the mast to a windless apparatus at the bottom thereof for raising and lowering the lighting fixtures that are affixed to the luminaire ring encircling the top of the mast. Releasable support means are provided adjacent the upper portion of the mast to engage the luminaire ring and support the weight of the lighting fixtures in their raised position. The releasable support means are out of reach of vandals. Signalling means are also provided to tell the operator below when the light carrying unit is in its proper locked position at the upper part of the mast. The releasable support means is controlled by a release cable that extends to the bottom of the mast and is secured inside the base.